The present invention relates to a magnetic film comprising an amorphous magnetic thin film having an easy magnetizing axis perpendicular to a plane of substrate, and the preparation thereof.
Especially, the present invention relates to a perpendicular magnetization film comprising an amorphous magnetic thin film suitably used as a high density magnetic storage as so-called perpendicular magnetic storage, opto-magnetic storage, or the like.
Hitherto, a cobalt thin film containing chromium of a little less than 20 atomic % has been investigated for a perpendicular magnetic storage. A thin film composed of an alloy of cobalt and chromium prepared by a sputturing method, and the like is known to be capable of recording high density-information and to be corrosive resistant.
The maximum value of the perpendicular uniaxial anisotropy constant Ku of the above-mentioned alloy film of cobalt and chromium is about 2.times.10.sup.6 erg/cm.sup.3. In order that an easy magnetizing direction is perpendicular to substrate, a relationship Ku-2.pi.Ms.sup.2 &gt;0 must be satisfied, wherein Ms indicates saturation magnetization. As a result, the maximum value of Ms of a perpendicular magnetization film of an alloy of cobalt and chromium is about 700 gausses.
For reading a stored information, an intensity of a detected signal is considered to be proportional to Ms. Thus, a larger Ms brings a favarable magnetic storage.
An alloy of samarium and cobalt, that is, a composite of SmCo.sub.5, constitutes a hexagonal crystal, where c-axis is a direction of easy magnetization, and the uniaxial magnetic anisotropy constant reaches to a level of 10.sup.8 erg/cm.sup.3. In an amorphous alloy of samarium and cobalt, a large anisotropy is also expected. By turning an easy axis of the thin amorphous film to the perpendicular direction to the substrate, one can obtain a perpendicular magnetization thin film of large Ms. In addition, a large anisotropy of a magnetic thin film causes a large coercive force. Therefore, it realizes the stabilities of written information bits.
However, when a deposition of an alloy of samarium and cobalt is performed using an ordinary method such as electron-beam-evaporation or sputtering, the easy magnetizing direction is readily parallel to the substrate. Thus a perpendicular magnetization film cannot be obtained. Recently it is recognized that a perpendicular magnetization film can be prepared in sputtering by applying a negative bias voltage to the substrate. However, in that method, another circuit for supplying a voltage must be provided since a substrate is an insulator in most cases, so that the preparation process becomes complicated. More than anything else, a perpendicular magnetization film cannot be obtained by way of registance heating- or electron beam heating-evaportion.
An object of the present invention is to provide a perpendicular magnetization film without any applying a bias voltage in its preparation process.